Angioplasty systems are well known. A typical system includes a syringe coupled to a balloon catheter to be placed in a patient's blocked artery or the like. The balloon is inserted into an artery or vein and manipulated by a physician through the vascular system until the balloon is in the vicinity of the blockage. Fluid is then forced from the syringe into the balloon to inflate the balloon and compress the material blocking the artery against the walls of the artery to unblock the blood vessel. The balloon is then deflated and removed from the patient.
It has long been appreciated that to avoid injury to the patient the angioplasty balloon should not be inflated for too long a period of time or to too great a pressure. To monitor the pressure in the balloon, electronic monitors have been used with angioplasty systems that digitally display the pressure, typically in atmospheres, within the balloon as sensed by an electronic pressure transducer placed in fluid communication with the balloon. The electronic pressure transducer generates an electrical pressure signal corresponding to the pressure in the balloon. The electrical pressure signal is coupled over wires to conversion circuitry in the electronic monitor which typically compares the electric pressure signal to a reference value with the difference therebetween being representative of the actual pressure in the balloon. The conversion circuitry converts that difference into a numerical value for display on the digital numerical read-out.
One drawback with such conventional electronic angioplasty systems is the inability to verify that the conversion circuitry is working properly and thus that the displayed pressure is correct. While systems for blood pressure transducers have been developed to test the reliability of the wires to the monitor and of the pressure transducer itself in its operating environment, such as that disclosed in U.S. Pat. No. 4,760,730, systems to verify operation of the monitor's conversion circuitry is typically not usable in the operating environment of the angioplasty system. Such testing is inconvenient and removes the monitor from use for possibly a significant period of time. For example, to verify the operation of the conversion circuitry, the entire monitor usually must be sent to an electronics lab for testing.
Another drawback with such conventional electronically monitored angioplasty systems is that the physician must watch the pressure read-out to confirm that the balloon is completely deflated. For example, to avoid ischemia or other problems associated with extended pressure times or high pressures, the angioplasty balloon needs to be deflated to relax the blood vessel. Conventional systems require the physician to avert his attention to the pressure display to confirm balloon deflation which means the doctor risks being at least temporarily unaware of the patient's appearance or condition.